This invention relates to a process for introducing fluid feeds to pressurized reactors. This invention also concerns an apparatus capable of effecting such introduction. In one of their more specific aspects, the process and apparatus of this invention relate to the manufacture of H.sub.2 and CO containing gaseous products, e.g., synthesis gas, reducing gas and fuel gas, by the high pressure partial oxidation of carbonaceous slurries.
Processes for and apparatuses used in the pressurized partial oxidation of carbonaceous slurries are both well known in the art. See, for example, U.S. Pat. No. 4,113,445; U.S. Pat. No. 4,353,712; and U.S. Pat. No. 4,443,230. In most instances, a carbonaceous slurry and an oxygen-containing gas are fed to a reaction zone which is at a temperature of about 2500.degree. F. (about 1370.degree. C.). Bringing the reactor up to such a temperature can be achieved by at least two methods. In one of the methods, a simple preheat burner is affixed, in a non-airtight manner, to the reactor's burner port. This preheat burner introduces a fuel gas, e.g., methane, into the reaction zone to produce a flame sufficient to warm the zone to a temperature of about 2000.degree. F.-2500.degree. F. (about 1090.degree. C.-1370.degree. C.) at a rate which does not do harm to the reactor refractory material. Generally, this rate is from about 40 F. .degree./hr (about 22 C. .degree./hr) to about 80 F. .degree./hr (about 44 C. .degree./hr). During this preheat stage, the reaction zone is kept at ambient pressure or slightly below. The less than ambient pressure is desirable as it causes air to enter the reaction zone through the non-airtight connection between the preheater and the reactor, which air is then available for use in combusting the fuel gas. After the desired preheat temperature is achieved, the preheat burner is removed from the reactor and is replaced by the process burner. This replacement should occur as quickly as possible as the reaction zone will be cooling down during the replacement time. Cool downs to a temperature as low as 1800.degree. F. (982.degree. C.) are not uncommon. If the reaction zone is still within an acceptable range, the carbonaceous slurry and the oxygen-containing gas, with or without a temperature moderator, are fed through the process burner to achieve partial oxidation of the slurry. Care must be taken to prevent raising the reaction zone temperature too quickly with the process burner as thermal shock can damage the reactor's refractory material.
If the reaction zone temperature is below the acceptable temperature range, the preheat burner must then be placed back into service. In these instances, process time is lost and additional labor expense is realized.
The other of the two methods for bringing up the reaction zone temperature to within a desirable range entails the use of a dual-purpose burner which is capable of acting as a preheat burner and as a process burner; see, for example, the burner disclosed in U.S. Pat. No. 4,353,712. This type of burner provides conduits for selective and contemporaneous feeding of carbonaceous slurry, oxygen-containing gas, fuel gas and/or temperature moderators. When the burner is used for preheating the reactor, the burner feeds the oxygen-containing gas and the fuel gas in the proper proportions to achieve complete combustion. After the reactor temperature is within the desired range, the fuel gas can either be replaced completely by the carbonaceous slurry or co-fed with the slurry. When the co-feeding mode is used, generally the fuel gas feed is reduced so that there will only be partial oxidation occurring. Co-feeding is usually used when initially introducing the carbonaceous slurry to the reactor and when maintaining reactor temperature until process conditions can be equilibrated for the carbonaceous slurry/oxygen-containing gas feed mode of operation. While the use of a dual-purpose burner does not suffer from the loss in process time and the additional labor expenses of the preheat burner/process burner method, it is not without its own drawbacks. When using the dual-purpose burner, the maintenance of flame stability under both preheat conditions, i.e., ambient pressure-complete oxidation, and process conditions, i.e., high pressure, partial-oxidation, is difficult and can result in lowering of process reliability.
Some in the synthesis gas industry have proposed using the combination of a preheat burner and a process burner in which the latter is capable of providing a selective contemporaneous feed of carbonaceous slurry, oxygen-containing gas, fuel gas and/or temperature moderators. While this combination may still entail the loss of process time and the realization of labor costs associated with replacing the preheat burner with the process burner, the selective contemporaneous feed feature of the process burner is used to reduce the before-discussed thermal shock to the reactor refractory material. The reduction in thermal shock is achieved by bringing the reaction zone temperature from its cooled-down temperature, after preheat burner removal, back up to the desired temperature by initially using a feed of oxygen and fuel gas and then gradually replacing the fuel gas with the carbonaceous slurry. By gradually increasing the carbonaceous slurry fuel, there is less of the slurry liquid to heat and vaporize and thus a minimization of reactor temperature drop. Further, during the initial period of carbonaceous slurry feed, the continued feeding of the fuel gas results in the addition of heat to the reactor. The fuel gas is combusted under partial oxidation conditions so that there is little contamination by CO.sub.2, etc., of the gas product.
For a process burner to be useful in the just-described procedure, it must be capable of providing to the reactor, in an efficient manner, the oxygen-containing gas and both the carbonaceous slurry and the fuel gas. Efficiency demands that the carbonaceous slurry be evenly dispersed in the oxygen-containing gas and be in a highly atomized state, e.g., having a maximum droplet size less than about 1000 microns. Both uniform dispersion and atomization help insure proper burn and the avoidance of hot spots in the reaction zone.
It is therefore an object of this invention to provide a process and a process burner which is capable of providing selective and contemporaneous feed to a reaction zone of three or more fluids in which one of the fluids is highly atomized and well dispersed in at least one of the remaining fluids.